The present invention involves a new and improved method of removing and installing valve springs, particularly for use on internal combustion engines with a rocker arm stud or bolt located adjacent to the valve spring.
Internal combustion engines generally use a plurality of valves on each cylinder to provide means for introducing a fuel-air mixture into the cylinder and means for exiting exhaust gases after combustion. Typically, these valves are mounted on the cylinder head and consist of a valve face which extends into the cylinder and a valve stem which extends through and above the cylinder head. A valve spring is positioned about the valve stem above the cylinder head. The valve spring is held under a compression load by means of a valve spring keeper and a valve spring keeper lock which engages the valve stem thereby holding the valve in a raised and therefore closed position. In operation, the valve is reciprocated thousands of times per minute by means of a rocker arm pivotally mounted on a rocker arm stud or bolt. One end of the rocker arm engages the top of a push rod linearly positioned opposite the rocker arm stud or bolt from the valve stem. The other end of the rocker arm engages the top of the valve stem. As the push rod pivots the rocker arm, the rocker arm reciprocates the valve by alternately pushing down upon the valve stem, thereby further compressing the valve spring, and then releasing this downward force, thereby allowing the valve spring to return the valve to the closed position. It is this reciprocating motion of the valve which causes wear and failure of the component parts of the valve assembly often requiring the removal and installation of the valve spring to make the necessary repairs.
While the prior art discloses various tools for the removal and installation of valve springs, most tend to be complex, of limited application, require the removal of additional component parts of the engine, may cause damage to other component parts of the engine or any combination thereof. U.S. Pat. No. 3,363,302 issued to Haselmo on Jan. 16, 1968, and U.S. Pat. No. 4,567,634 issued to Landry on Feb. 4, 1986, both rotate using a part of the engine assembly, particularly a rocker arm stud, as the pivot point. This pivot action subjects the rocker arm stud to rotational forces it was not designed to carry, as well as sliding the inside edge of the tool over the rocker arm stud threads as the tool is rotated, any of which may cause damage to the rocker arm stud and/or the rocker arm stud threads. It is a further disadvantage of these tools that other component parts of the engine will interfere with the operation of the tool, specifically the push rod corresponding to the valve spring being worked upon must be removed or the engine rotated to lower such push rod to provide sufficient clearance for the tool to operate and, in the case of the Landry tool, all rocker arms in front of the valve spring being worked upon must be removed to provide the necessary clearance.
U.S. Pat. No. 5,689,870 issued to Robey on Nov. 25, 1997, uses the push rod as the pivot point to compress the valve spring. This requires the engine to be rotated such that the push rod is placed in the optimum position for the tool to operate. It is a further disadvantage of this tool that, as the valve spring is compressed, the threads on the rocker arm stud are subjected to both sheer and rotational forces as the crank down nut is rotated against the force of the valve spring thereby creating the possibility of damage to such threads. In addition, in the event that the operator should leave the tool with the valve spring in the compressed position for an extended period of time, the constant force transmitted through the push rod to a hydraulic lifter, as most engines are so equipped, may cause oil to bleed from the hydraulic lifter thereby creating the potential for internal damage to the engine when it is next started. Finally, this tool is not adaptable for use with high performance valve springs which are significantly longer than standard valve springs and may not be used with the cylinder head removed from the engine.
U.S. Pat. No. 5,349,732 issued to Spence on Sep. 27, 1994, discloses a locking jaw plier-like tool. The length of this tool may require other significant component parts of the engine to be removed before the tool can be utilized while the cylinder head is mounted on the engine such as, depending upon the particular installation, the intake manifold, the power steering pump, the alternator or some other significant component part. In addition, this tool would subject the rocker arm stud to certain rotational forces thereby creating the possibility of bending the rocker arm stud. Finally, this tool discloses interchangeable jaws to fit various applications thereby increasing the complexity and cost of the tool as a whole.
U.S. Pat. No. 4,262,403 issued to Wilhelm and Bellino on Apr. 21, 1981, and U.S. Pat. No. 4,780,941 issued to Tucker on Nov. 1, 1988, both disclose complex, and therefore expensive, tools of limited application. Both of these tools may be used only with rocker arm studs and therefore could not be used on applications utilizing rocker arm bolts. It is a further disadvantage of the Wilhelm/Bellino tool that it is not adjustable for different spring heights and therefore will not work with high performance valve springs. It is a further disadvantage of the Tucker tool that it will be very slow in compressing the valve spring and further, do to certain rotational loads, may cause damage to the rocker arm stud.
Thus, there is a need for a simple and inexpensive tool which can quickly and easily remove and install valve springs on a wide variety of valve spring applications and which requires removal of only the minimum component parts of an engine to be used.